1. Field of the Invention
The present invention relates to a surface plasmon resonance biosensor, specifically, a measuring chip for the same and a method for producing the measurement chip.
2. Background Art
A number of methods using immunological reactions are used in clinical tests for detecting target substances. Conventional methods are known to be intricate and require labeling substances. Thus, immunological sensors using a surface plasmon resonance biosensor (SPR) is being used, in which no labeling substance is required and a ligand can be detected with high sensitivity. This surface plasmon resonance biosensor is based on the phenomenon that the intensity of a monochromatic light reflected from the interface between an optically transparent substance such as glass and a metal thin-film layer is dependent on the refractive index of a sample placed on the reflecting side of the metal. Accordingly, a sample can be analyzed by measuring the intensity of the reflected monochromatic light.
An optical part of a measuring cell for this surface plasmon resonance (surface plasmon resonance biosensor) has a structure shown in FIG. 2. Namely, porous material 5 is formed on metal thin-film 2 formed on glass substrate 1, and physiologically active substance 4, such as an enzyme or antibody, is retained or immobilized on the surface or inside of porous material 5. Examples of porous material 5 to be used include weaved, knitted or non-woven cloths made of synthetic fibers, natural fibers, inorganic fibers or the like, and porous inorganic or organic materials (see Japanese Patent Laid-open No. 164195/1991). Furthermore, carboxymethyl dextran is used as a porous material in a commercial product (BIAcore 2000, Pharmacia Biosensor).
However, physiologically active substance 4 just exists on the surface of porous material 5 and interacts with target substances.
LB (Langmuir-Blodgett) method is occasionally used to immobilize physiologically active substance 4 on metal thin-film 2 (see Japanese Patent Laid-open No. 288672/1993). However, this method has a disadvantage in that LB membrane binds poorly to a metal thin-film and peels off together with the physiologically active substance.
Furthermore, Japanese Patent Laid-open No. 264843/1997 discloses measuring cells for a surface plasmon resonance biosensor.
The present inventors have now found that sensitivity of a measuring chip for a surface plasmon resonance sensor is extremely improved when only a small amount of a physiologically active substance is immobilized on a specific plasma polymerization layer.
An objective of the present invention is to provide a measuring chip for a surface plasmon resonance sensor that can detect a small amount of target substances in high sensitivity.
Another objective of the present invention is to provide a measuring cell for a surface plasmon resonance sensor that can detect a small amount of target substances in high sensitivity.
Further objective of the present invention is to provide a method for producing said measuring chip.
The present invention provides a measuring chip for a surface plasmon resonance sensor comprising a metal layer and one or more plasma polymerization layers formed on said metal layer.
The present invention also provides a measuring chip for a surface plasmon resonance sensor comprising a metal layer, one or more plasma polymerization layers formed on said metal layer, and a biologically active substance immobilized on the surface of said plasma polymerization layer.
The present invention also provides a measuring cell for a surface plasmon resonance sensor comprising said measuring chip.
The present invention also provides a method for producing a measuring chip for a surface plasmon resonance sensor comprising the steps of forming a metal layer on an optically transparent substrate, forming one or more plasma polymerization layers on said metal layer, and then immobilizing a biologically active substance on the surface of said plasma polymerization layer.